# std::get_if (std::variant)

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< cpp‎ | utility‎ | variant

Defined in header `<variant>` |  |
| (1) | (since C++17)
template< std::size_t I, class... Types > constexpr std::add_pointer_t<std::variant_alternative_t<I, std::variant<Types...>>> get_if( std::variant<Types...>* pv ) noexcept; |  |
template< std::size_t I, class... Types > constexpr std::add_pointer_t<const std::variant_alternative_t<I, std::variant<Types...>>> get_if( const std::variant<Types...>* pv ) noexcept; |  |
| (2) | (since C++17)
template< class T, class... Types > constexpr std::add_pointer_t<T> get_if( std::variant<Types...>* pv ) noexcept; |  |
template< class T, class... Types > constexpr std::add_pointer_t<const T> get_if( const std::variant<Types...>* pv ) noexcept; |  |

1) Index-based non-throwing accessor: If pv is not a null pointer and pv->index() == I, returns a pointer to the value stored in the variant pointed to by pv. Otherwise, returns a null pointer value. The call is ill-formed if `I` is not a valid index in the variant.
2) Type-based non-throwing accessor: Equivalent to (1) with `I` being the zero-based index of `T` in Types.... The call is ill-formed if `T` is not a unique element of Types....

### Template parameters

I | - | index to look up
Type | - | unique type to look up

### Parameters

pv | - | pointer to a variant

### Return value

Pointer to the value stored in the pointed-to variant or null pointer on error.

### Example

Run this code

    #include <iostream>
    #include <variant>

    int main()
    {
        auto check_value = [](const std::variant<int, float>& v)
        {
            if (const int* pval = std::get_if<int>(&v))
                std::cout << "variant value: " << *pval << '\n';
            else
                std::cout << "failed to get value!" << '\n';
        };

        std::variant<int, float> v{12}, w{3.f};
        check_value(v);
        check_value(w);
    }

Output:

    variant value: 12
    failed to get value!

### See also

get(std::variant) (C++17) | reads the value of the variant given the index or the type (if the type is unique), throws on error (function template)

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